Method and system for transmission of carrier signals between first and second antenna networks

ABSTRACT

Method and system for transmission of carrier signals, each of which occupy a different radio-frequency band, between first and second antenna networks ( 14, 15 ), each comprising a plurality of distributed antenna&#39;s ( 6 ), with the first antenna network ( 14 ) being coupled to a main coupling device ( 3 ) and to an intermediate coupling device ( 21 ), the second antenna network ( 15 ) being coupled to the intermediate coupling device ( 21 ), and with the coupling devices ( 3, 21 ) being coupled to one or more peripheral devices ( 8, 22 ), wherein the intermediate coupling device ( 21 ) is controlled to have a carrier signal frequency band of the second antenna network ( 15 ) occupied by a carrier signal which is exchanged with a peripheral device ( 8 ) which is coupled to the main coupling device ( 3 ) or with a further peripheral device ( 22 ) which is coupled to the intermediate coupling device ( 21 ).

FIELD OF THE INVENTION

The invention relates to a method and transmission system for couplingeach of one or more peripheral devices to a network of distributedantennas wherein each peripheral device can transmit one or more carriersignals, which occupy a different radio frequency band.

A method and a system of the type mentioned above are known frompractice.

BACKGROUND

It is observed that wide frequency bands may be allocated to differentsystems, such as GSM and UMTS. In each of such systems smaller frequencysubbands may be allocated to different telephone companies. Each of saidsubbands may contain several carriers or carrier signals havingdifferent carrier frequencies and being allocated to different parts ofthe premises or buildings where the method and system are applied.

Occasionally it may occur that a carrier signal interferes with acarrier signal transmitted by a source or antenna outside the presentsystem. Further, one may want to expand the antenna network while usingtherein carrier signals having radio-frequency bands which may or maynot differ from those already used or associated with differentperipheral devices. Until now, to achieve this the coupling of carriersignals to the main transmission path required the application of a maincoupling device designed and equipped to handle such expansion or thecoupling device needed to be replaced by such more complex couplingdevice. When deploying carrier signals having radio-frequency bandswhich are in use already, the main coupling device must be designed tohave a plurality of ports for connection to a plurality of cables ofseparate antenna networks accordingly. In fact the system of the typehaving one such port, as mentioned above, is just duplicated. A majordrawback of modifying or replacing the coupling device is that at leastpart of the system is out of operation then. Another drawback is thatequipment for deploying additional carrier signals must be installed inthe proximity of the coupling device, which may be difficult orimpossible to do because of limited space, cooling restrictions andhigher power demands.

SUMMARY

It is an object of the invention to solve the disadvantages of the priorart method and system.

Accordingly, the system is made flexible for the use of carrier signalswith different radio-frequency bands in different antenna network partsand/or the use of identical radio-frequency bands in different antennanetworks associated with different peripheral devices. The intermediatecoupling device may suitably be identical for use with any configurationor distribution of carrier signals among different antenna networkparts. Thus, the intermediate coupling device may be standardizedaccording to frequency band allocation to telephone companies and maytherefore reduce costs of production, sales and reconfiguration. Theintermediate coupling device may be installed at a location which isremote from the main coupling device, which may save transmission powerand may reduce the demands for space and cooling on beforehand.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the drawings, inwhich:

FIG. 1 shows a diagram of a prior art transmission system;

FIG. 2 shows a diagram of a transmission system according to theinvention;

FIG. 3 shows a diagram of an intermediate coupling device of the systemshown in FIG. 2;

FIG. 4 shows in further detail a first embodiment of a switch node ofthe intermediate coupling device shown in FIG. 3;

FIG. 5 shows in further detail a second embodiment of a switch made ofthe intermediate coupling device shown in FIG. 3;

FIG. 6 shows in further detail a third embodiment of a switch node ofthe intermediate coupling device shown in FIG. 3 with no furtherperipheral device connected thereto;

FIG. 7 shows the third embodiment of a switch node with a furtherperipheral device connected thereto; and

FIG. 8 shows the third embodiment of a switch node with a furtherperipheral device through a one-directional line.

DETAILED DESCRIPTION OF THE INVENTION

The prior art transmission system shown in FIG. 1 comprises a maincoupling device 3, a network 4 of a plurality of antenna's 6 and abranched cable 7 which connects the main coupling device 3 to theantenna's 6, and one or more peripheral devices 8 which are connected tothe main coupling device 3. A peripheral device 8 represents a sourceand/or destination for a one or more signals from a plurality ofpossible carrier signals, which each occupy a different radio-frequencyband. The main coupling device 3 couples the carrier signals used in thesystem to a main transmission path provided by cable 7 for feedingcarrier signals from peripheral devices 8 to the antenna's 6. Inaddition, the main coupling device 3 distributes carrier signalsreceived from the antenna's 6 over said main transmission path toperipheral devices 8.

Usually the antenna's 6 of the network 4 will be distributed over thepremises of a company or institution. The antenna's may be distributedinside or outside several buildings. There may also be othertransmission systems with similar or dissimilar antenna arrangementsnearby.

Some carrier signals may be interfered from other signals, such ascarrier signals used in other nearby transmission systems. Yet,interference may occur only for a part of antenna network 4, for exampleonly relating to antenna's 6 installed in or on upper floors of abuilding and only for some of the carrier signals. Therefore one maywant to use different carrier signals in different parts of the antennanetwork 4. To that extent one could apply separate antenna networks ofwhich the branched cables are connected to different ports of a maincoupling device. In that case the main coupling device can be consideredto consist of separate devices each having one port connected to a cableof an antenna network. This is like having the system shown in FIG. 1duplicated. In case duplicated coupling devices are installed in thesame cabinet such arrangement requires long cables to antenna networkswhich are not closest to the coupling devices, which will be cumbersomeand costly to install and which may require increased transmission powerand receiving sensitivity of the coupling devices. In addition, sucharrangement may cause problems as to power and cooling requirements.

As observed before, carrier signals for use with the system are signalslike those of GSM and UMTS services which can be allocated to andhandled by different communication service providers or telephonecompanies. Therefore several and different peripheral devices 8 may beused, depending on communication services to be offered and demands bycommunication service providers. In any case, a number of ports of themain coupling device 3 which can be connected to peripheral devices 8will be limited. Therefore any modification of the system which requiresthe addition of a peripheral device 8 above said limited number of portswill require modification of main coupling device 3, if not replacementthereof. Doing so will have the system go down for a significant timewhich, apart from the modification or replacement of main couplingdevice 3, will be inconvenient to users and may incur further costs.

With the transmission system according to the invention, as shown inFIG. 2, the antenna network 4 of the prior art system is split into orexpanded to more than one antenna networks 14, 15, which comprisebranched cables 17, 18 respectively and antenna's 6. Using the inventionthe split may be effective only for certain carrier frequencies, leavingthe others completely undisturbed. Just like branched cable 7 of theprior art system shown in FIG. 1, branched cable 17 of the system shownin FIG. 2 is connected to one or more peripheral devices 8 through amain coupling device 3. Branched cables 17 and 18 are connected to eachother by an intermediate coupling device 21 which is connected also toone or more further peripheral devices 22, which may be of the same typeas a peripheral device 8. In this description the term “intermediate”means “in between” rather than precisely halfway.

Branched cables 17 and 18 provide first and second main transmissionpaths respectively.

Intermediate coupling device 21 is arranged to exchange carrier signalsbetween the second antenna network 15 and the main coupling device 3 orbetween the second antenna network 15 and the one or more furtherperipheral devices 22.

Intermediate coupling device 21 will be described in further detail withreference to FIGS. 3 and 4.

FIG. 3 shows a diagram of the intermediate coupling device 21 and itcomprises a first splitter/combiner 31, a second splitter/combiner 32and a plurality of switches 33, which could be electronic switches. Asplitter/combiner 31, 32 is preferably composed of a bank of filters.FIG. 4 shows a diagram of a switch 33.

One port of splitter/combiner 31 is connected to branched cable 17 ofthe first antenna network 14 of the system shown in FIG. 2. One port ofsplitter/combiner 32 is connected to branched cable 18 of the secondantenna network 15 of the system shown in FIG. 2. Each splitter/combiner31, 32 derives carrier signals carried by the branched cable 17, 18respectively connected therewith and feed the derived carrier signalsinto transmission paths 35, 36 of a first group and a second group ofintermediate transmission paths coupled to splitter/combiner 31, 32respectively. The splitter/combiners 31, 32 is preferably frequencyselective to subbands assigned to different telephone companies. Eachswitch 33 is connected to an intermediate transmission path 35 of thefirst group, an intermediate transmission path 36 of the second groupand to a further peripheral device 22, if existent, by a cable 38.

Apart from splitting a main transmission path provided by cables 17 and18 into intermediate transmission paths 35, 36 for different carriersignals the splitter/combiners 31, 32 are arranged to combine carriersignals from intermediate transmission paths 35, 36 to a composed signalfor transmission over cable 17, 18 respectively.

As shown in FIG. 4, a first embodiment of a switch 33 comprises a dualtwo-way switch 42. One common terminal 43 is connected to anintermediate transmission path 35 of the first group of intermediatetransmission paths. A second common terminal 44 is connected to a cable38. In a first position of switch 33 (or 42), as shown in FIG. 4, theintermediate transmission path 35 of the first group is connected to aline termination or terminator 45 and cable 38 is connected to saidintermediate transmission path 36 of the second group. In a secondposition of switch 33 (or 42) the intermediate transmission path 35 ofthe first group is connected to the intermediate transmission path 36 ofthe second group and cable 38 is connected to a terminator 46.

Terminators 45 and 46 are line terminating members, which each mayconsist of a simple resistor.

From the above it will be clear that the intermediate coupling device 21is suitable to have a carrier signal frequency band of the secondantenna network 15 occupied by a carrier signal exchanged between thefirst and second antenna networks 14, 15 or between a further peripheraldevice 22 and the second antenna network 15.

The intermediate coupling device 21 is suitable to be manufactured asstandard device for use with different configurations of a systemaccording to the invention with different numbers of peripheral devices22.

Preferably switches 33, in particular switches 42 thereof, areelectronic switches, so that any modification of the use of carriersignal frequency bands can be carried out by remote control. Such remotecontrol of an electronic switch may be provided by a peripheral device22 as associated with said switch, with the further peripheral device 22having appropriate remote control functionality.

FIG. 5 shows a second embodiment of a switch 33. The second embodimentof FIG. 5 differs from the first embodiment of FIG. 4 by that switch 42is replaced by a swap-type switch 47 having common terminals 48 and 49connected to the intermediate path 35 and line 38 respectively.Dependent on being in either one of its two positions switch 47 connectsintermediate path 35 to intermediate path 36 and cable 38 to terminator46 or intermediate path 35 to terminator 46 and cable 38 to intermediatepath 36. As shown in FIG. 5, said second embodiment needs only oneterminator.

As shown in FIG. 6 a third embodiment of a switch 33 comprises acirculator 50 having three ports 51, 52, 53, which are connected tointermediate path 35, cable 38 and intermediate path 36 respectively. Acirculator is known per se. A signal which is input at an input portthereof may circulate in a circulation direction 54 from the input portto subsequent ports.

As shown in FIG. 6 a short circuit 56 is applied to the second port 52of circulator 50. A signal fed from intermediate path 35 into thecirculator 50 through the first port 51 will enter the second port 52,will be reflected by the short circuit 56, re-enter port 52 and thanleave the circulator 50 through the third port 53 into the secondintermediate path 36.

As shown in FIG. 7, with respect to FIG. 6 the short circuit 56 has beenreplaced by a further peripheral device 22. An output/input of thefurther peripheral device 22 connected to cable 38 presents a matchedimpedance with respect to cable 38. The matched impedance of the furtherperipheral device 22 will absorb a signal coming from the firstintermediate path 35 through the first and second ports 51, 52 and cable38. A signal delivered by the further peripheral device 22 to the secondport 52 of circulator 50 will arrive at the third port 53 and will enterthe second intermediate path 36.

Therefore, dependent on connecting a short circuit 56 or a furtherperipheral device 22 to the second port 52 of circulator 50 thisconfiguration operates as a switch for entering a signal into the secondintermediate path 36 from the first intermediate path 35 or from thefurther peripheral device 22.

As shown in FIG. 8 a one-directional line 58 may be connected in cable38 between the further peripheral device 22 and the second port 52 ofcirculator 50. The one-directional line 58 operates as an isolator forprotecting the further peripheral device 22 against a signal from thefirst intermediate path under worst case circumstances. Theone-directional line 58 could be another circulator with the second portterminated by a matched load.

1. A method for coupling each of one or more peripheral devices to anetwork of distributed antennas, each peripheral device being suitablefor transmission of one or more carrier signals, which each occupy adifferent radio frequency band, the network of antennas comprising amain transmission path by cable, in which the carrier signals arecoupled into and out of the main transmission path from and to theperipheral devices respectively, comprising the steps of a) dividing thenetwork of antennas into a first network and a second network comprisinga first main transmission path part and a second main transmission pathpart of the main transmission path respectively an intermediate couplingdevice being coupled to the first and second main transmission pathparts; and at a location between the first and second main transmissionpath parts: b) splitting the first main transmission path part into afirst group of intermediate transmission paths or transmission ofdifferent carrier signals over different intermediate transmission pathsof the first group; c) splitting the second main transmission path partinto a second group of intermediate transmission paths for transmissionof different carrier signals over different intermediate transmissionpaths of the second group; and d) connecting an intermediate path of thesecond group to an intermediate path of the first group or to a furtherperipheral device.
 2. The method according to claim 1, wherein anintermediate path of the first group of intermediate paths is connectedto an intermediate path of the second group of intermediate paths or toan intermediate path terminating member.
 3. The method according toclaim 2, wherein an input of the intermediate coupling device forconnection to the further peripheral device is connected to anintermediate path of the second group of intermediate paths or to anintermediate path terminating member.
 4. A transmission system,comprising a main coupling device and a network of distributed antennashaving a cable providing a main transmission path, the main couplingdevice being suitable for coupling the cable to one or more peripheraldevices, each of which being suitable for transmission of one or morecarrier signals, which each occupy a different radio frequency band,wherein the network of antennas being divided into first and secondnetworks providing first and second main transmission path parts of themain transmission path respectively, an intermediate coupling devicebeing coupled to the first and second main transmission path parts andsplitting the first and second main transmission path parts into a firstand second groups of intermediate paths respectively for transmissionper group of intermediate paths of different carrier signals overdifferent intermediate transmission paths, and the intermediate couplingdevice connecting an intermediate path of the second group to anintermediate path of the first group or to a further peripheral device.5. The transmission system according to claim 4, wherein a path of thefirst group of intermediate paths is connected to a path of the secondgroup of intermediate paths or to an intermediate path terminatingmember.
 6. The transmission system according to claim 5, wherein aninput of the intermediate coupling device for connection to the furtherperipheral device is connected to an intermediate path of the secondgroup of intermediate paths or to an intermediate path terminatingmember.
 7. The transmission system according to claim 6 wherein theintermediate paths of the first and second groups of intermediate pathsand the further peripheral device are connected to each other by remotecontrollable electronic switches.
 8. The transmission system accordingto claim 7, wherein remote control of the electronic switches isexercised by control functionality of a peripheral device which isassociated with the switch.
 9. The transmission system according toclaim 4, wherein a first port of circulator is connected to a firstintermediate path, a second port is connected to a short circuit or to afurther peripheral device, and a third port of the circulator isconnected to a second intermediate.
 10. The transmission systemaccording to claim 9, wherein with a further peripheral device connectedto the second port of circulator the further peripheral device providesa matched load to said second port.
 11. The transmission systemaccording to claim 10, wherein with a further peripheral deviceconnected to the second port of circulator the further peripheral deviceis connected to said second port through an isolator which provides amatched load to said second port.
 12. The transmission system accordingto claim 11, wherein the isolator is a further circulator of which anintermediate or second port is terminated by a matched load.